It is recommended that you assign a verb to each action. Think about times when a bug might return to an earlier state in the workflow. Model these negative actions. For example, a QA engineer might reject a developer’s claim, which returns an issue to Development.
You may also uncover missing positive actions while considering each way that an issue can travel. For example, you realize that QA engineers also reject some issue reports, in effect closing the issues. In the example diagram below, the Reject Bug action by a QA engineer leads to the Not-a-Bug state. Ensure that all actions eventually lead to a terminal state.